Substantial technological advances have been made in the stage lighting field. For example, it is not uncommon for a single stage light to include dimmers for light intensity control, color filter arrays for providing numerous colored lights, selectable gobo silhouettes, moveable lens assemblies, in addition to lamp pan and tilt actuators. Moreover, microprocessors have been utilized to maintain an account in RAM memory of the positional aspect of each of the features, as well to control the actuation of each of the noted features. Modern stage lights are controlled by large scale integration circuitry and feedback systems, not a lot unlike other processor-controlled apparatus.
Notwithstanding the many features which may be incorporated into a stage light, the primary purpose is to provide an intense beam of light onto the subject matter of a performance. Tungsten filament lamps have been found to operate very effectively in providing an intense light beam which is rich in colors over the visible light spectrum. This is essential when using filters so that various wavelengths may be selected to produce light beams of desired colors. Other types of lamps have been used with equal effectiveness.
According to commercially available lamps suitable for stage lighting purposes, a large filament current is required to produce a highly intense light beam. As a result, a substantial amount of power is consumed which must be dissipated as heat within the stage light. It is not uncommon to use a four hundred watt lamp in a stage light instrument. Of these four hundred watts of power used by the light, it is not unusual to generate two hundred watts of heat energy. It is also not uncommon for the immediate environment of such a stage lamp to reach a temperature of 250.degree. C. (482.degree. F.). This temperature is a result of the tungsten filament temperature which typically reaches 2900.degree. C. Generally, with operating temperatures of this range, only quartz bulb envelopes can be used.
In addition to the heat generated by the high wattage lamp, additional heat is generated by power supplies and the digital circuitry. From the foregoing, the significance of an adequate, reliable and quiet operating cooling system can be appreciated. As a very real and practical danger, a failure in the cooling system of a stage light can literally result in the melting of the internal components of the lamp instrument.
One approach utilized for cooling a studio floodlight is illustrated in U.S. Pat. No. 3,959,644. In this patent, a pretensioned stainless steel tape is unwound from a reel into a cylindrical passage through which air is passed to cool the lamp. The complicated and expensive mechanical nature of the cooling system of the noted patent is not well adapted for reliable use, nor is such a structure cost effective for use in large systems having in excess of several hundred lamps.
From the foregoing, it may be seen that a need has arisen for a cost effective lamp instrument cooling system. There is an associated need for an improved cooling system in lamp instruments having sophisticated digital circuitry and associated power consuming apparatus.